An organic electroluminescent device, also known as organic light emitting diode (OLED) device, is a new kind of display technology, and the OLED device has become a future trend of display device market with its advantages such as high brightness, abundant colors, low-voltage DC driving and simple preparation process and so on.
Generally, the OLED device employs a rigid glass substrate or a flexible polymer substrate as a carrier, and is formed by depositing an anode and a cathode as well as an organic light emitting layer therebetween. The organic light emitting layer typically includes a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer and an electron injection layer and so on. The organic light emitting layer is very sensitive to oxygen and water vapor; if the oxygen and water vapor permeate into the organic light emitting layer, it will cause many undesirable phenomena such as black dot, needle hole, electrode oxidization, chemical reaction of organic materials and so on, which can severely affect a service life of the OLED device. Therefore, a packaging technology is a key of realizing industrialization of OLED.
Inventors find that a commonly used packaging technology is a thin-film packaging technology, which is based on a multilayer structure alternating between an organic polymer thin film and an inorganic thin film prepared by a vacuum coating process. With high density, the inorganic thin film is a main layer to barrier water and oxygen. But the inorganic thin film has less elasticity and greater internal stress, while the organic polymer thin film has higher elasticity, resulting in easy separation between the inorganic thin film and the organic polymer film, so the water and oxygen may invade into the organic light emitting layer, which can severely affect the service life of OLED device.